High frequency system



March 1, 1938. P. s. CARTER HIGH FREQUENCY SYSTEM Filed July 13, 1955 7 I 1 r0 mmI/rrm J 2 E19. 2 MAP r0 TRANSMITTER J 2 1 I Z l l 4 u mwars 6 CONTROL 6 45/105 I F 5 r0 TRANJM/TTER To m/vsM/rrm J 1 INVENTOR P.5. CA TER ATTORNEY Patented Mar. 1, 1938 PATENT OFFICE HIGH FREQUENCY SYSTEM Philip S. Carter, Port Jefferson,

N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application July 13, 1935, Serial 8 Claims.

This invention relates to a method of and apparatus for matching the impedance of a high frequency transmission line circuit and load deis adapted to radiate any one of a plurality of diiferent frequencies supplied to it over a transmission line.

The primary object of the invention is to enable the matching of impedances in a high frequency load circuit whereby a plurality of frequencies may be used alternatively on the circuit with high efliciency.

A further object is to provide a single antenna system which can be used for radiating a plurality of difierent frequencies without disturbing the adjustments of the system for the frequencies not in use.

involves considerable delay and labor. These disadvantages are overcome, according to the present invention which enables an immediate change in adjustment for a predetermined change in frequency, through the intermediary of switching mechanism.

In general, the invention consists in first matching the impedance of the line and high frequency load for the lowest frequency, and then,

switch is employed to disconnect the elements used for matching the impedance of the line and load for the higher frequency when only the lower frequency is employed. In this manner it is only necessary to open the switch when the at the lower frequency and close it for operation at the higher frequency, assuming that only two frequencies are employed. Any number of frequencies can, of course, be employed using the same principles.

Figs. 1-4, inclusive, illustrate different embodiments of the invention.

Referring to Fig. 1, there is shown conventionally in box form,

line 2 supplying high frequency currents from a transmitter, not shown. In order to match the line 2 and load I, for use with either of two frequencies, the system is first excited at the lower frequency and by means of a reactance 3,

here shown as a coil by way of example only,

placed at a predetermined point across the line 2,

and having a desiredovalue, the impedance is matched in accordance with the principles out-' lined in my Patent No. 1,909,610, granted May 16,

1933. Coil 3 is then left permanently in the position shown and the antenna is excited at the higher of the two frequencies, and the complete circuit including antenna I, line 2 located between coil 3 and the antenna, matched to the line by means tion of this coil is determined the theory outlined in my United States Patents 1,909,610, supra, and 2,019, granted November 5, 1935. Switch 4 is provided for disconnecting coil 5 from the line and system when it is desired to use the lower frequency.

It will be appreciated, of course, that when the line is first matched for the lower frequency by cuit 5. It is preferred however that the location of the circuits 3 and 5 be as shown in the drawing.

Fig. 2 discloses a sections 6 in place of the concentrated reactances 3 and 5, and a remote control relay or motor 8 for operating switch 4.

Fig. 3 illustrates the system of the invention modification employing line i means of the switches when only the lowest frequency is used, and the third circuit is disconnected when only the second frequency is used.

In Fig. 4 is shown a system similar to that of Fig. 1, except that double line sections are employed in the place of the concentrated reac-' tances. Such arrangements of double line sections and their manner of calculation and use, are disclosed in my United States Patent No. 2,019,809, supra, to which reference is made for a more detailed description thereof.

It will be appreciated, of course, that condensers may be used instead of the reactance coils shown. It is also to be understood that the word reactance recited in the specification and claims is intended to cover both concentrated reactances and line sections having uniformly distributed constants and combinations of these.

What is claimed is:

1. In combination, a high frequency load adapted for operation on a plurality of different frequencies, a transmission line connecting said load to high frequency apparatus, a reactance permanently bridged across said line and so spaced from the load as to match the impedance of said line and load for one frequency to be used thereby, another reactance bridged across said line and so spaced from said first reactance as to match the combined impedance of said load and first reactance for a higher frequency to be used, and a switch for disconnecting said second reactance from said line whenever the lower frequency is used.

2. A system in accordance with claim 1 characterized in this, that said switch and second reactance for the higher frequency are farther removed from the load than said first reactance.

3. In a high frequency system adapted for use on at least two different frequencies, said system having a load and a transmission line connected to said load, the method of operation which includes the steps of first matching the impedance of the load to the line at the lower of the two frequencies by inserting a reactance across said line at a predetermined location, subsequently matching the combined impedance of the load and reactance at the higher of the two frequencies while said system is also matched for the lower frequency by inserting another reactance across said line at another predetermined location, and disconnecting the: last reactance when using only the lower frequency.

4. A system in accordance with claim 1, including remote control means for operating said 55 switch.

5. In combination, a high frequency load adapted for operation on a plurality of different frequencies, a transmission line connecting said load to high frequency apparatus, a reactance permanently bridged across said line and so spaced from the load as to match the impedance of said line and load for one frequency to be used thereby, another reactance bridged across said line and so spaced from said first reactance as to match the combined impedance of said load and first reactance for a higher frequency to be used, a switch for disconnecting said second reactance from said line whenever the lower frequency is used, and remote control means for operating said switch, said reactances being in the form of line sections having uniformly distributed capacity and inductance.

6. A system in accordance with claim 1, characterized in this, that said reactances are in the form of lumped inductances.

'7. In combination, a high frequency load adapted for operation on a plurality of different frequencies,- a transmission line connecting said load to high frequency apparatus, a reactance permanently bridged across said line and so spaced from said load as to match the impedance of said line and load for one frequency to be used thereby, another reactance bridged across said line and so spaced from said first reactance as to match the combined impedance of said load and first reactance for a higher frequency to be used, a switch for disconnecting said second reactance from said line whenever the lower frequency is used, and still a third reactance bridged across said line and so spaced from the other reactances as to match the combined impedance of said load and first and second reactances for a still higher frequency to be used, and a switch for disconnecting said third reactance from said line whenever any one of the lower two frequencies is used.

8. In combination, a high frequency antenna adapted for operation on a plurality of different frequencies, a transmission line connecting said antenna to a source of signals, means bridged across said line and so spaced from said antenna as to match the impedance of said line and antenna for one frequency to be used thereby, additional means bridged across'said line and so spaced from said first means as to match the combined impedance of said antenna and first means for a higher frequency 'to be used, and means for effectively disconnecting said additional means from said line whenever the lower frequency is used;

PHILIP S. CARTER. 

